栈是一个逻辑结构，通俗的讲，是一个有“纪律”的线性表，栈只允许一端进行插入和删除操作，即“先进后出”规则。如下图所示：
红箭头代表栈顶，即只允许插入和删除的那一端。绿箭头代表栈底，是固定的，即不允许进行插入和删除的另一端。当这个栈内没有元素时，则此时该栈被称为空栈。同样的，栈也有初始化，判定是否为空，插入（进栈），删除（出栈）等操作。下面是关于栈的python实现。
顺序栈实现：
#coding:utf-8 ''' author:xzfreewind ''' #顺序存储 class Stack(object): #初始化一个栈 def __init__(self,size): self.size = size self.num = 0 self.stack = [] #获取栈的长度 def getSize(self): return self.num #输出栈 def outStack(self): for l in self.stack: print l #进栈 def appendStack(self,value): if self.num >= self.size: print "the stack is full" return else: self.stack.append(value) self.num += 1 #出栈 def popStack(self): if self.isEmpty(): print "the stack is empty,no element can be output" return else: topElement = self.stack[-1] self.stack.remove(topElement) return topElement def isEmpty(self): if self.num == 0: return True else: return False def isFull(self): if self.num == self.size: return True else: return False链栈实现：
#链式对象建立 class Node(object): def __init__(self,vaule,q=0): self.value = vaule self.next = q #链式存储 class chainStack(object): #初始化链栈 def __init__(self): self.head = 0 #判断栈是否为空 def isEmpty(self): if self.head == 0: return True else: return False #计算栈的长度 def getSize(self): length = 0 p = self.head while p != 0: length += 1 p = p.next return length #将数组初始化成栈存储 def initStack(self,list): self.head = Node(list[0]) node = self.head for i in list[1:]: p = Node(i) p.next = node node = p #进栈 def insert(self,value): if self.head == 0: #如果为空栈，直接插入 self.head = Node(value) else: node = Node(value) node.next = self.head self.head = node #出栈 def pop(self): if self.head == 0: #如果为空栈，提示栈为空 print "the stack is empty" return else: l = self.head.value self.head = self.head.next return l #输出栈 def outStack(self): if self.head == 0: #如果为空栈，提示栈为空 print "the stack is empty" return p = self.head while p != 0: print p.value p = p.next